Client-side mixing for VOIP conferences

Hi,

I would like to know if any one has any experience or pointers to research papers or white papers on Client-Side mixing for voip conferences. I am doing some research on voip security and need to avoid sharing keys with the conference mixer. I have learnt that TeamSpirit from Spirit DSP provides functionality to do Client-Side mixing - I am looking for some implementation experiences wrt the same in terms of bandwidth required, client side implementation overhead or other specifics.

Any inputs on the same will be appreciated.

Thanks! Sunitha.